The PS pressure switch is an input to the idle valve controller. There is also an input for the AC compressor clutch. The idle controller looks at engine speed, temperature, and those other inputs and then modulates the valve to get to the desired speed. The modulation is based on providing a pulsed current to the valve coil. The duty cycle is increased to open the valve further.  

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Alistair Bell
Sent: Tuesday, January 3, 2017 10:03 PM
To: vanagon@GERRY.VANAGON.COM
Subject: PS Pump switch high idle question

Hi,

Can someone school me on the way the PS pump switch affects the idle speed? I have a faint idea that it somehow changes the pulse to the ICV, I'm supposing it results in a balance that has the ICV open longer.

Thanks

Alistair